Stackable roller carriage having swingably mounted wheels

ABSTRACT

A rollercarriage having a carriage bottom below which a plurality of wheels ( 3, 5 ) is mounted, at least one of the wheels being mounted swingably about a substantially vertical swivel axis ( 7 ) which does not intersect the axis for the rotation of the wheel. The roller carriage is moreover provided with retention means to retain the at least one swingably mounted wheel ( 5 ) on an overlying roller carriage. The retention means comprise a support face ( 8 ) which supports the swingably mounted wheel at a support point ( 18 ), an outer engagement area ( 16 ) extending at least partly about the swivel axis ( 7 ), and an inner engagement area ( 16 ) positioned between the swivel axis ( 7 ) and the outer engagement are ( 16 ), said outer and inner engagement areas restricting the rolling movement of the at least one swingably mounted wheel ( 5 ) on an overlying roller carriage. At least one of the engagement areas is provided with at least one projection capable of engaging the swingably mounted wheel ( 5 ) on an overlying roller carriage, so that the rotation of the swingably mounted wheel about the support point ( 18 ) on the support face ( 8 ) is essentially prevented.

The invention relates to a roller carriage.

Such a roller carriage is known from EP B1 675 829, which discloses aroller carriage having a carriage bottom below which a plurality ofwheels is mounted, at least one of these being swingably mounted about avertical swivel axis. The upper side of the roller carriage is providedwith means capable of retaining the wheels of an overlying rollercarriage when several roller carriages are stacked. For the fixedwheels, these retention means are formed by rectangular recesses inwhich the fixed wheels can stand stably, while for each of the swingablymounted wheels they are formed by a completely or partly annular guidetrack with outer and inner engagement areas which retain the swingablymounted wheels against rotation.

Roller carriages of this type are usually used for the transport ofgoods in the distribution network from a wholesaler to retailers. Theroller carriages are then transported back to the wholesaler in theempty state, it being a widespread wish that the roller carriages can bestacked so as to take up as little space as possible during transport.

The roller carriage described in the above-mentioned European patentsolves a general problem of roller carriages having swingably mountedwheels, viz. that normally the wheels have to be aligned in specificdirections in order to be retained in recesses provided in the upperside of the underlying roller carriage. The stated solution allows theorientation of the swingably mounted wheels to be quite arbitrary, whilestill providing satisfactory retention of the wheels.

However, in particular for the roller carriages in which the statedguide track is formed by a bracket plate, it has been found that a stackof many roller carriages, e.g. as many as 20, may be unstable in spiteof the good retention against rotation of the swingably mounted wheels,it being possible for the swingably mounted wheels to rotate slightlyabout the point where they stand on the bracket plate. The effect ofthis is the greater, the more roller carriages are stacked on top ofeach other, and the greater the risk is for the persons working with theroller carriages.

The object of the present invention is to provide a solution in whichthis instability is avoided.

This is achieved by constructing a roller carriage having a bottomframe, with a plurality of wheels on its lower surface, at least one ofthe wheels being swingably mounted so as to swing about a substantiallyvertical swivel axis that does not intersect an axis of rotation of thewheel. The bottom frame also has retention means on its upper surface toretain at least one swingable wheel of an overlying roller carriage. Theretention means include a support face for supporting the wheel of theoverlying roller carriage at a support point that is positioned on acircular arc concentric with the swivel axis of the wheel. The retentionmeans also includes an outer engagement area extending at least partlyaround the swivel axis of the wheel, and an inner engagement areadisposed between the swivel axis of the wheel and the outer engagementarea. The outer and inner engagement areas cooperate to restrict rollingmovement of the swingable wheel of the overlying roller carriage in adirection transverse to the axis of rotation of the of the wheel. Inaddition, at least one of the inner and outer engagement areas isprovided with at least one projection adapted to engage the wheel, theprojection being adapted to absorb forces in parallel with the axis ofrotation of the wheel at a radial distance from the support point suchthat swinging of the wheel about the support point on the support faceis essentially prevented for substantially any angular orientation ofthe wheel with respect to the projection.

This provides a roller carriage which supports each of the swingablymounted wheels on an overlying roller carriage at at least two points,viz. at the point on the rolling face of the wheel which stands on thesupport face of the bracket plate, and at a point along the inner and/orouter engagement areas. Hereby, increased retention of the swingablymounted wheels against rotation about the swivel axis is obtained.

As a result of this increased retention, a quite stable stack of rollercarriages can be obtained.

When the outer and inner engagement areas are arranged along concentriccircles a particularly effective retention is obtained, as these canhereby normally support the swingably mounted wheels quite optimallyagainst rotation in their rolling direction entirely independently ofthe angular orientation of the wheel.

The projection or projections which are to retain a swingably mountedwheel, may either be provided in connection with the inner engagementarea or in connection with the outer engagement area.

The projection preferably consists of a pin or the like in connectionwith the inner engagement area, capable of engaging a groove which isprovided in the rolling face of the swingably mounted wheel.

Alternatively, or as a supplement, several projections may be arrangedin connection with the outer engagement area, and these are preferablyarranged so that their mutual distance either corresponds to the widthof the wheel, or so that they can engage an annular groove provided inthe rolling face of the wheel.

The invention will now be explained more fully with reference to thedrawing, in which

FIG. 1 is a lateral view of a roller carriage according to theinvention,

FIG. 2 is a top view of a roller carriage according to the invention,

FIG. 3 shows a corner of the roller carriage shown in FIG. 1,

FIG. 4 shows the same as FIG. 2, but with a wheel having an annulargroove arranged thereon,

FIGS. 5 and 6 show alternative embodiments of the invention.

FIG. 1 shows a roller carriage 1 from the side. The roller carriage 1comprises a bottom frame 2 below which two fixedly oriented, freelyrevolving wheels 3 are mounted by means of forks 4 secured to the bottomframe 2 by welding or bolting. The roller carriage also has twoswingably mounted wheels 5 arranged at the opposite end of the rollercarriage 1. The swingably mounted wheels 5 are secured to wheel forks 6which are swingably secured about a swivel axis 7 to a wheel bracket orsupport face 8. The support face 8 is welded to the bottom frame 2, aswill appear from the following.

FIG. 2 is a top view of the roller carriage 1 of FIG. 1, and it will beseen that the bottom frame 2 comprises an outer rectangular frameconsisting of two long sides and two end sides. This outer frame is madeof a bent pipe profile welded together at the ends. A transom 9 issecured between the long sides of the outer frame, which transom partlyimparts rigidity to the roller carriage and partly serves as anattachment part for the support faces 8. The support faces 8 consist ofa plate-shaped material which is welded to the transom 9 and the endside of the roller carriage, respectively. In the embodiment shown, theswingably mounted wheels 5 are mounted on the underside of the supportface 8 by means of bolts which extend through four holes 10 in thesupport face.

The bottom frame 2 additionally comprises a transom 11, which likewiseimparts rigidity to the bottom frame 2, but also serves as an attachmentpart for the fixedly oriented wheels 3.

A grating is arranged between the two transoms 9 and 11, said gratingbeing welded to the transoms 9, 11 and the long sides of the bottomframe 2. The grating also imparts rigidity to the bottom frame 2 andsimultaneously serves as an access restriction to the interior of theroller carriage 1, but is otherwise without importance to the inventionas such.

Brackets 12, which may be an integral part of the wheel forks 4 for thefixedly oriented wheels 3 or form an attachment part for these, aresecured at the corners at one end of the roller carriage 1 between theend side of the bottom frame 2 and the transom 11. The brackets 12 areprovided with a recess 13 whose ends are provided with support faces 14for the fixedly oriented wheels 3 of a roller carriage arranged on topof the roller carriage 1.

As mentioned, support faces 8, whose structure will be described morefully below with reference to FIG. 3, are arranged at the other end ofthe bottom frame 2.

FIG. 3 shows an enlarged view of one of the corners of the rollercarriage 1, and the long side and the end side of the bottom frame 2,the support face 8, the transom 9 and the ends of the rods for thegrating are clearly visible.

As mentioned before, the support face 8 is welded to the end side of thebottom frame 2 and the transom 9 and is moreover provided with holes 10for mounting of a swingably mounted wheel 5, which, however, is notshown in FIG. 3. The sides 15 of the support face 8 are bent downwardsto provide additional strength and rigidity against deflection.

The upper side of the support face 8 has mounted thereon an outerengagement area 16 in the form of a ring made of bent flat iron, and aninner engagement area 17 in the form of an upwardly protruding pin. Bothengagement areas are welded to the support face 8.

The effect of these outer and inner engagement areas 16, 17 is to retainan arbitrarily oriented, swingably mounted wheel 5 on an overlyingroller carriage, as described in EP B1 675 829.

According to the present invention, the inner engagement area, in thepreferred embodiment shown, is formed such that it can engage aswingably mounted wheel 5 on an overlying roller carriage. The reason isthat the inner engagement are 17 is formed as a pin whose upper Dart isconically inclined, and whose shape fits an annular groove which isprovided in the rolling face of the swingably mounted wheel 5. This isshown more fully in FIG. 4, which substantially corresponds to FIG. 3,but with a swingably mounted wheel 5 from an overlying roller carriage.

The wheel 5, from which a portion has been removed to show itscross-section, stands on the support face 8 at the support point 18 andis retained against rotation by the outer and inner engagement areas 16and 17. In addition, the inner engagement area 17 in the form of a pinengages an annular groove 19 which is provided in the rolling face ofthe wheel 5. This engagement between the pin and the wheel 5 preventsthe wheel 5 from rotating about the support point 18. This results in amore stable stacking than can be obtained with the roller carriageaccording to EP B1 675 829, which reduces the risk of personal injurywhen working with many roller carriages stacked on top of each other.

In order to fit the upper conical part of the pin the groove 19 isformed with inclined sides. This shape of the groove 19 moreover has theadvantage that dirt and soil do not easily stick in the groove if theroller carriage is used on a dirty substrate.

In the shown embodiment, the outer engagement area 16 consists of bentflat iron, but it may be constructed in many other ways, e.g. as a ringof wire material as shown in EP B1 675 829.

FIGS. 5 and 6 schematically show two other embodiments of the invention,where the outer engagement area 16 is arranged to engage the swingablymounted wheel 5 on an overlying roller carriage.

In FIG. 5, the outer engagement area 16 is shown with a plurality ofprojections 20, whose mutual distance corresponds to the width of thewheel 5. In this embodiment, the wheel 5 does not have to provided withan annular groove, which means that conventional wheels may be used.

Also FIG. 6 shows a number of projections 21 provided on the outerengagement area 16. These projections are shaped so as to mate with anannular groove provided in the rolling face of the wheel 5. The innerengagement area 17 consists of a pin, as shown in FIGS. 3 and 4. Thus,in this embodiment, both the outer and the inner engagement areas engagethe wheel 5 on an overlying roller carriage.

The mutual distance between the projections 21 corresponds to the widthof the wheel 5 in the embodiment shown in FIG. 6, so that the wheel 5can also be retained between the projections 21 in the same manner asshown in FIG. 5.

To ensure correct positioning of the wheel 5, the projections 20 and 21shown in FIGS. 5 and 6 must be formed such that the wheel 5 is guideddown to a correct position either between the projections 20 or with thegroove around one of the projections 21. This may be obtained by makingthe projections 20, 21 pointed upwardly, so that their side faces serveas guide faces for the wheel 5.

The invention has been described in the foregoing with reference to aroller carriage which is welded together of steel profiles/plates.

However, nothing prevents the invention from also being worked inconnection with other types of roller carriages, e.g. roller carriagesmade of plastics. The invention can also be worked using a combinationof steel and plastics, e.g. in that the bottom frame of the rollercarriage, as such, is made of welded steel profiles, while the inner andouter engagement areas are made of plastics which are subsequentlymounted on the bottom frame.

Nor do the inner and outer engagement areas have to extend over 360°either, like in the preferred embodiment, but may e.g. extend over 270°or less, if so desired.

What is claimed is:
 1. A roller carriage comprising: a bottom framehaving an upper and a lower surface, said bottom frame comprising aplurality of rotatable wheels disposed on said lower surface, at leastone of said wheels being swingable about a substantially vertical swivelaxis that does not intersect an axis of rotation of said at least onewheel, and retention means disposed on said upper surface, saidretention means being adapted to retain at least one swingable wheel ofan overlying roller carriage, said retention means comprising a supportface adapted to support the at least one swingable wheel of theoverlying roller carriage at a support point said support point beingpositioned on a circular arc concentric with a swivel axis of the atleast one swingable wheel of the overlying roller carriage, saidretention means further comprising an outer engagement area extending atleast partly around the swivel axis of the at least one swingable wheelof the overlying roller carriage outside said circular arc, and an innerengagement area disposed inside said circular arc, wherein said outerand inner engagement areas cooperate to restrict a rolling movement ofthe at least one swingable wheel of the overlying roller carriage in adirection transversely to an axis of rotation of the of the at least oneswingable wheel of the overlying roller carriage, at least one of saidinner and outer engagement areas is provided with at least oneprojection adapted to engage the at least one swingable wheel of theoverlying roller carriage, said projection being adapted to absorbforces in parallel with the axis of rotation of the at least oneswingable wheel of the overlying roller carriage at a radial distancefrom said support point such that a swing of the at least one swingablewheel of the overlying roller carriage about the support point on thesupport face is essentially prevented for substantially any angularorientation of the wheel on said support point with respect to said atleast one projection, and all of said at least one projection that areprovided on said inner engagement areas are inside said circular arc,and all of said at least one projection that are provided on said outerengagement area are outside said circular arc.
 2. A roller carriageaccording to claim 1, wherein said at least one projection is proximatethe swivel axis of the at least one swingable wheel of the overlyingroller carriage.
 3. A roller carriage according to claim 1, wherein saidat least one swingable wheel defines an annular groove in a rolling facethereof, and wherein said least one projection is disposed on said innerengagement area, and wherein said at least one projection is adapted toengage an annular groove in a rolling face of the at least one swingablewheel of the overlying roller carriage.
 4. A roller carriage accordingto claim 2, wherein said at least one projection comprises an upwardlyprotruding pin.
 5. A roller carriage according to claim 4, wherein saidpin is a rotation-symmetrical pin comprising an upper end that isinclined conically inwards.
 6. A roller carriage according to claim 1,wherein said outer engagement area comprises a plurality of projections,wherein adjacent projections are spaced from one another by a distancethat substantially corresponds to a width of the at least one swingablewheel of the overlying roller carriage.
 7. A roller carriage accordingto claim 1, wherein said at least one swingable wheel defines an annulargroove in a rolling face thereof, and wherein said outer engagement areacomprises a plurality of projections adapted to engage an annular groovea rolling face of the at least one swingable wheel of the overlyingroller carriage.